Active equipment protection methods and apparatus

ABSTRACT

Systems and methods are described for communications networks. A method, includes deploying a communication link, at least a portion of which is protected against active equipment failure, that includes a splitter-combiner communicatively coupled between a data drop/add device and a headend. The systems and methods provide advantages because a communication network can be protected, at least in-part, against active equipment (e.g., data drop/add device) failure, passive equipment (e.g., optical fiber) failure, and/or equipped for non-intrusive expansion of the network.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to the field of communicationnetworks. More particularly, the invention relates to the use ofsplitter-combiners in ring communication networks.

[0003] 2. Discussion of the Related Art

[0004] Communication nodes are designed and used for point to pointcommunications over a network. A communications node is a transmittingand receiving (TX/RX) source.

[0005] Stringing a plurality of nodes together into a ring network iswell known to those skilled in the art of communications. What is alsowell known is that an interruption in communication service can be bothinconvenient and costly.

[0006] For instance, a conventional ring network is shown in FIG. 1,where a physical bus logical ring is depicted with three nodes 110, 120,130 communicatively coupled to a headend. Each of the nodes 110-130includes a data drop/add device 125. Node 110 is physically connected tonode 120 with a pair of optical fibers 140. Node 120 is physicallycoupled to node 130 with a further pair of optical fibers 150. FIG. 1indicates by dashed line segments that additional nodes may bepositioned between nodes 120 and 130.

[0007] Another instance of a conventional ring network is shown in FIG.4, where a ring architecture is depicted with three nodes 410, 420, 430communicatively coupled to a headend. As above, each of the nodes410-430 includes the data drop/add device 125. However, node 420 isphysically connected to node 410 with a single optical fiber 440.Similarly, node 430 is physically coupled to node 420 with a singleoptical fiber 450. FIG. 4 indicates by dashed line segments thatadditional nodes may be positioned along fiber 450 between nodes 420 and430.

[0008] A disadvantage of either of the instances shown in FIGS. 1 and 4is that a break one of the optical fiber lines can prevent all of thenodes from bidirectionally communicating with the headend. Therefore,what is required is solution that provides the network with at leastsome protection in the event of a break in one of the fiber lines.

[0009] One approach to providing some protection in the event of a breakin one of the fibers in the past has been to connect the nodes togetherwith redundant parallel fibers. A break in one fiber can then beovercome through the use of a parallel redundant fiber. However, adisadvantage of this approach has been relatively high cost. Therefore,what is also needed is a solution that provides some protection in theevent of a fiber break in a more cost-effective manner.

[0010] Another problem with this technology has been that expansion of aring network requires interruption of communication services. Adding anode to the ring requires that the ring be broken, at least temporarily,so that the new node can be inserted into the ring. This break in thering can prevent all of the nodes from bidirectionally communicatingwith the headend until the installation is complete. In many commercialsettings, such a temporary interruption to install additional nodes isunacceptable. Therefore, what is also required is a solution thatpermits the network to be expanded without interrupting communicationservice.

[0011] Another problem with this technology has been failure of activeequipment along the ring. If one of the data drop/add devices fails, allof the nodes can be prevented from bidirectionally communicating withthe headend. Therefore, what is also required is a solution thatprovides protection in the event of active equipment failure.

[0012] Heretofore, the requirement(s) of protection in the event of aline break, expandability without interruption, and protection in theevent of active equipment failure, referred to above have not been fullymet. What is needed is a solution that addresses at least one, andpreferably all, of these requirements. The invention is directed tomeeting these requirements, among others.

SUMMARY OF THE INVENTION

[0013] A goal of the invention is to simultaneously satisfy theabove-discussed requirements of network protection in the event of aline break, expandability without communications interruption, andnetwork protection in the event of active equipment failure which, inthe case of the prior art, are not satisfied, much less simultaneouslysatisfied. Another goal of the invention is to satisfying one or two ofthese requirements.

[0014] One embodiment of the invention is based on an apparatus,comprising a communications link, said communications link including asplitter-combiner communicatively coupled to a headend, saidsplitter-combiner including: a signal splitter communicatively coupledto a headend input and communicatively coupled to a downstream output;and signal combiner communicatively coupled to said signal splitter,communicatively coupled to an upstream input, and communicativelycoupled to a headend output. Another embodiment of the invention isbased on a method, comprising deploying a communications link at least aportion of which is protected against signal conductor failure, whereindeploying includes providing said communications link with asplitter-combiner that is communicatively coupled to a headend. Anotherembodiment of the invention is based on a method, comprising deploying acommunications link with non-intrusive expansion capability, whereindeploying includes providing said communications link with asplitter-combiner communicatively coupled to a headend.

[0015] Another embodiment of the invention is based on an apparatus,comprising a communications link, said communications link including asplitter-combiner communicatively coupled to a headend, saidsplitter-combiner including: a signal splitter communicatively coupledto a headend input and communicatively coupled to a downstream output;and signal combiner communicatively coupled to said signal splitter,communicatively coupled to an upstream input, and communicativelycoupled to a headend output; and a data drop/add device communicativelycoupled to said downstream output and communicatively coupled to saidupstream input. Another embodiment of the invention is based on anapparatus, comprising a communications link, said communications linkincluding a first splitter-combiner communicatively coupled to aheadend, said first splitter-combiner including: a first signal splittercommunicatively coupled to a first headend input and communicativelycoupled to a first downstream output; and a first signal combinercommunicatively coupled to said first signal splitter, communicativelycoupled to a first upstream input, and communicatively coupled to afirst headend output; a data drop/add device communicatively coupled tosaid first downstream output and communicatively coupled to said firstupstream input; a second splitter-combiner communicatively coupledbetween said first headend input and said headend, said secondsplitter-combiner including: a second signal splitter communicativelycoupled to said headend and communicatively coupled to a seconddownstream output; and a second signal combiner communicatively coupledto said second signal splitter, communicatively coupled to a secondupstream input, and communicatively coupled to said first headend input.Another embodiment of the invention is based on a method, comprisingdeploying a communication link, at least a portion of which is protectedagainst active equipment failure, that includes a splitter-combinercommunicatively coupled between a data drop/add device and a headend.

[0016] These, and other goals and embodiments of the invention will bebetter appreciated and understood when considered in conjunction withthe following description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingpreferred embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A clear conception of the advantages and features constitutingthe invention, and of the components and operation of model systemsprovided with the invention, will become more readily apparent byreferring to the exemplary, and therefore nonlimiting, embodimentsillustrated in the drawings accompanying and forming a part of thisspecification, wherein like reference characters (if they occur in morethan one view) designate the same parts. It should be noted that thefeatures illustrated in the drawings are not necessarily drawn to scale.

[0018]FIG. 1 illustrates a schematic view of a conventional physicalbus, logical ring, appropriately labeled “PRIOR ART”.

[0019]FIG. 2 illustrates a schematic view of a physical bus, logicalring with each node includes a splitter-combiner which can provide fiberprotection and/or non-intrusive expansion, representing an embodiment ofthe invention.

[0020]FIG. 3 illustrates the physical bus, logical ring of FIG. 2 afterthe non-intrusive addition of a fourth node having a splitter-combiner,representing an embodiment of the invention.

[0021]FIG. 4 illustrates a schematic view of a conventional ringarchitecture, appropriately labeled “PRIOR ART”.

[0022]FIG. 5 illustrates a schematic view of a ring architecture witheach node including a splitter-combiner, which can provide activeequipment protection, representing an embodiment of the invention.

[0023]FIG. 6 illustrates a more detailed schematic view of the A/D nodesdepicted in FIGS. 1-5, appropriately labeled “PRIOR ART.”

[0024]FIG. 7 illustrates a schematic view of a physical bus, logicalring architecture with each A/D node including two splitter-combiners, afirst of which can provide active equipment protection and a second ofwhich can provide fiber protection and/or non-intrusive expansion,representing a combined embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] The invention and the various features and advantageous detailsthereof are explained more fully with reference to the nonlimitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description of preferred embodiments.Descriptions of well known components and processing techniques areomitted so as not to unnecessarily obscure the invention in detail.

[0026] The context of the invention includes communication networks.Expected applications include physical bus, logical rings. Expectedapplications also include ring architectures.

[0027] The invention can include placing a splitter in the transmittingpath of a node and another splitter in the receiving path of the samenode. In the case of optical signal splitting, the splitters can bereadily commercially available fiber optic tap couplers. In the case ofelectrical signal splitting, the splitters can be simple Y branches. Ineither case, two of the splitters can be coupled together to compose asplitter-combiner. In this coupled configuration one of the splittersfunctions as a combiner. The splitter-combiner in-turn defines a shuntand a bypass.

[0028] By providing signals combined from the bypass with a gain of fromapproximately 10 dB to approximately 20 dB relative to signals combinedfrom the shunt, a switching functionality is provided by thesplitter-combiner. If a signal is present on the bypass, this bypasssignal will be detected. If no signal (or only a very weak signal) ispresent on the bypass, the shunt signal will be detected. It isimportant to appreciate that signals being transmitted along the shuntare overwhelmed by signals being transmitted along the bypass, if thelater are present.

[0029] The splitters that compose the splitter-combiner can be opticalin the case of an optical communications network. Alternatively, thesesplitters can be electrical in the case of an electrical communicationsnetwork. Further, these splitters could even be vibrational in the caseof an acoustical communications network. Other types of splitters couldbe used.

[0030] Preferred embodiments of the invention can use a passivesplitter-combiner. In the case of an optical network, a passive splittercombiner can include two fiber optic couplers. The use of a passivesplitter-combiner confers major advantages. There is no need formechanical or electrical switching. There is no need for faultdetection. There is no need for monitoring. There are fewer componentscompared to an active device. There is no switch to fail. There is noswitching time.

[0031] The invention can include protecting at least a portion of anetwork against failure of signal connection lines. For example, given aphysical bus, logical ring, each node can be provided with asplitter-combiner. If a signal connection line fails, thesplitter-combiner that is RX relative the failed line will switch todetecting signals from the shunt. In this way, at least part of thenetwork can be protected from the affect of the failed line. This can betermed fiber protection.

[0032] The splitter-combiners do not have to be located in the samechassis as the data drop/add devices, or even the same nodes. Thesplitter combiners can be located in-between nodes. Preferredembodiments of the invention use a passive splitter-combiner device toshunt the communications route around the failed line.

[0033] Referring to FIG. 2, a physical bus, logical ring is depictedwith a first node 210, a second node 220 and a third node 230, each ofwhich includes a data drop/add device 125. FIG. 2 indicates by dashedline segments that additional nodes may be positioned between nodes 220and 230.

[0034] A splitter-combiner 250 is located within each of the nodes210-230. Each of the splitter-combiners 250 includes a signal splitter260 and a signal combiner 270 (see the detail numbers relating to thesplitter-combiner in the second node 220). The signal combiner 270 iscommunicatively coupled to the signal splitter 260.

[0035] Each of the signal splitters 260 is communicatively coupled to aheadend input 262 (see the detail numbers relating to the signalsplitter in the third node 230). Each of the signal splitters 260 iscommunicatively coupled to a downstream output 264.

[0036] Each of the signal combiners 270 is communicatively coupled to anupstream input 272 (see the detail numbers relating to the signalcombiner in the third node 230). Each of the signal combiners 270 iscommunicatively coupled to a headend output 274.

[0037] The path (connection) between the downstream output 264 and theupstream input 272 can be termed a bypass. The other path, typically ashorter path, between the signal splitter 250 and the signal combiner260 can be termed a shunt.

[0038] In this embodiment, the data drop/add device 125 of each node iscommunicatively coupled to the headend output 274 of the correspondingsignal combiner 270. Data flow is from the signal combiner to the datadrop/add device.

[0039] By providing the third node 230 with its splitter-combiner, animportant expansion feature is enabled. The addition of another node tothe third node 230 will be discussed below in more detail with regard toFIG. 3.

[0040] The invention can include adding a node to a network withoutinterrupting service to other nodes on the network. For example, given aphysical bus, logical ring, the last (terminal) node on the bus can beprovided with a splitter-combiner that will initially detect signalsfrom the shut. The additional node would then be connected to thesplitter-combiner. The additional node would then be the new terminalnode on the physical bus, logical ring. Upon connecting the additionalnode, the splitter-combiner in what was the terminal node will switch todetecting signals from the bypass. This can be termed non-intrusiveexpansion.

[0041] As above, the splitter-combiners do not have to be located in thesame chassis as the data drop/add devices, or even the same nodes.Preferred embodiments of the invention use a passive splitter-combinerdevice to bypass the communications route to the new terminal node.

[0042] Referring to FIG. 3, a fourth node 340, which includes anotherdata drop/add device 125, has been connected to the third node 230. Thesignal combiner in the fourth node 340 is communicatively connected tothe upstream input of the third node 230. Similarly, the signal splitterin the fourth node 340 is communicatively connected to the downstreamoutput of the third node 230.

[0043] Of course, additional nodes may be added to the fourth node 340.By providing the fourth node 340 with its splitter-combiner, the featureof non-intrusive expansion is still enabled.

[0044] The invention can include protecting at least a portion of a ringnetwork against failure of active equipment. For example, an activeequipment device can be isolated from the rest of the network byproviding the node with which the active device is associated with asplitter-combiner. If the active device fails, the associatedsplitter-combiner will switch to detecting the shunt signal, therebybypassing the failed device. This can be termed active equipmentprotection.

[0045] Again, although it can be advantageous to co-locate thesplitter-combiners with the data drop/add devices, thesplitter-combiners do not have to be located in the same chassis as thedata drop/add devices or even the same nodes. Since active equipment canfail for a number of reasons, notably power failure, preferredembodiments of the invention use a passive splitter-combiner device toshunt the communications route around the failed active device.

[0046] Referring to FIG. 5, a ring architecture is shown with a firstnode 510, a second node 520 and a third node 530, each of which includesa data drop/add device 125. FIG. 5 indicates by dashed line segmentsthat additional nodes may be positioned between nodes 520 and 530.

[0047] In this embodiment, the data drop/add device 125 of each node iscommunicatively coupled to the upstream input 272 of the correspondingsignal combiner 270. The data drop/add device 125 of each node is alsocommunicatively coupled to the downstream output 264 of thecorresponding signal splitter 260. Data flow is from the downstreamoutput 264 of the corresponding signal splitter 260 to the data drop/adddevice 125 and then to the upstream input 272 of the correspondingsignal combiner 270.

[0048] Referring now to FIG. 6, the data drop/add device 125 is depictedin a more detailed manner. The data drop/add device 125 includes anoptical receiver 610 (ORX). The optical receiver 610 can be anoptical-to-electronic transducer such as a charge-coupled device.Electrical circuit 620 is coupled to the optical receiver 610. Anoptical transmitter 620 (OTX) is coupled to the circuit 620. The opticaltransmitter can be an electronic-to-optical transducer such as a laserdiode.

[0049] The invention can also include combining two or more of fiberprotection, non-intrusive expansion, and/or active device protection. Tocombine these functionalities, two of the splitter-combiners can bejoined together to form a combined device. Again, preferred embodimentsof the invention use passive splitter-combiners. However, all aspects ofthe invention can be implemented with active splitter-combiners.

[0050] Referring to FIG. 7, a physical bus, logic ring is depicted witha first node 710, a second node 720 and a third node 730, each of whichincludes a data drop add device 125. Of course, additional nodes may belocated between the depicted nodes.

[0051] In this embodiment, each of the nodes includes twosplitter-combers 250. By coupling the headend output 274 of the firstsplitter-combiner to the headend input 262 of the second splittercombiner both of the features of fiber protection and active equipmentprotection are enabled. By providing the third node 730 with itssplitter-combiner, the feature of non-intrusive expansion is enabled.

[0052] The invention can also be included in a kit. The kit can includesome, or all, of the components that compose the invention. Morespecifically, the kit can include the splitter-combiner and othercomponents of the invention. The kit can also include a splicingequipment and supplies for retrofitting existing nodes with theinvention. The kit can contain a computer program. The kit can alsocontain instructions for practicing the invention and apparatus forcarrying out the invention. Unless otherwise specified, the components(and apparatus and/or instructions) of the kit can be the same as thoseused in the invention.

[0053] The invention can also utilize data processing methods thattransform signals from one state to another. For example, the inventioncan be combined with instrumentation to obtain state variableinformation on the detected signal(s) to actuate interconnected discretehardware elements. For instance, the invention can include monitoringthe switching state of the splitter-combiners and reporting their stateto the headend for recordation as diagnostic data. Further, theinvention can even include measuring the relative signal attenuationbetween the bypass and shunt to change the split ratio of the signalsplitters and/or signal combiners with variable filter, polarizersand/or refractive index devices, thereby lowering detected noise fromthe shunt during bypass operation while simultaneously maintainingsufficient shut sensitivity to meet the needs of a contingent switchingevent.

[0054] The term approximately, as used herein, is defined as at leastclose to a given value (e.g., preferably within 10% of, more preferablywithin 1% of, and most preferably within 0.1% of). The term coupled, asused herein, is defined as connected, although not necessarily directly,and not necessarily mechanically. The term deploying, as used herein, isdefined as designing, building, shipping, installing and/or operating.The term program or phrase computer program, as used herein, is definedas a sequence of instructions designed for execution on a computersystem. A program may include a subroutine, a function, a procedure, anobject method, an object implementation, an executable application, anapplet, a servlet, a source code, an object code, and/or other sequenceof instructions designed for execution on a computer system.

[0055] The particular manufacturing process used for fabricating thesplitter-combiner should be inexpensive and reproducible. Conveniently,the splitter-combiner of the invention can be fabricated using anysplicing method to join two Y branches, either optical or electrical. Inthe case of optical branches (e.g., tap couplers) it is preferred thatthe process be an optical butt splicing technique. For the manufacturingoperation, it is an advantage to employ a UV light curing, guide tubetechnique.

[0056] However, the particular manufacturing process used forfabricating the splitter-combiner is not essential to the invention aslong as it provides the described functionality. Normally those who makeor use the invention will select the manufacturing process based upontooling and energy requirements, the expected application requirementsof the final product, and the demands of the overall manufacturingprocess.

[0057] While not being limited to any particular performance indicatoror diagnostic identifier, preferred embodiments of the invention can beidentified one at a time by testing for the presence of sufficientsignal strength differential at the headend output of thesplitter-combiner. At the headend output of the splitter-combiner, thedifference in relative strength between signal(s) entering the head endinput and signal(s) entering the upstream input should be fromapproximately 10 dB to approximately 20 dB. This difference in relativestrength between the signals can be achieved by selecting the tapcoupling ratios (split ratios) of the signal splitter and the signalcombiner. This difference in relative strength can also be achieved byadjusting the amplitude of signals entering the headend input and theamplitude of signals entering the upstream input. The test for thepresence of sufficient signal strength differential can be carried outwithout undue experimentation by the use of a simple and conventionalsignal strength meter experiment.

EXAMPLES

[0058] Specific embodiments of the invention will now be furtherdescribed by the following, nonlimiting examples which will serve toillustrate in some detail various features of significance. The examplesare intended merely to facilitate an understanding of ways in which theinvention may be practiced and to further enable those of skill in theart to practice the invention. Accordingly, the examples should not beconstrued as limiting the scope of the invention.

Example 1

[0059] A physical bus, logical ring, can provide the fiber protectionand non-intrusive expansion functionalities where each add/drop (A/D)node includes a splitter-combiner. The splitter-combiner can include asignal splitter where approximately 5% of the signal energy is deflectedto the shunt and approximately 95% of the signal energy is directedtoward the bypass. Suitable fiber optic couplers with this output portratio are readily commercially available from E-TEK Dynamics, Inc.(models SWBC and/or SMFC); and Amphenol (part no. 945-271-C100). Thesplitter-combiner can include a signal combiner where approximately 50%of the combined signal energy is derived from the shunt, andapproximately 50% of the combined signal energy is derived from thebypass. Suitable fiber optic couplers are readily commercially availablefrom JDS Fitel (AC Series); E-TEK Dynamics, Inc. (models SWBC and/orSMFC); and Amphenol (part nos. 945-130-1000, 945-131-1000, 945-132-1000,945-170-1000, 945-171-1000 and/or 945-172-1000).

Example 2

[0060] A physical bus, logical ring, can provide the fiber protectionand non-intrusive expansion functionalities where each add/drop (A/D)node includes a splitter-combiner. The splitter-combiner can include asignal splitter where approximately 10% of the signal energy isdeflected to the shunt and approximately 90% of the signal energy isdirected toward the bypass. Suitable fiber optic couplers are readilycommercially available from JDS Fitel (AC Series); Amphenol (part nos.945-130-2000, 945-131-2000, 945-132-2000, 945-170-2000, 945-171-2000and/or 945-172-2000). The splitter-combiner can include a signalcombiner where approximately 10% of the combined signal energy isderived from the shunt, and approximately 90% of the combined signalenergy is derived from the bypass.

Example 3

[0061] The active equipment functionality can be provided by a ringarchitecture where each add/drop (A/D) node includes asplitter-combiner. The splitter-combiner can include a signal splitterwhere approximately 10% of the signal energy is deflected to the shuntand approximately 90% of the signal energy is directed toward thebypass. The splitter-combiner can include a signal combiner whereapproximately 10% of the combined signal energy is derived from theshunt, and approximately 90% of the combined signal energy is derivedfrom the bypass.

Practical Applications of the Invention

[0062] A practical application of the invention that has value withinthe technological arts is the non-intrusive expansion of communicationnetworks, such as adding a data drop/add node to a logical loop.Further, the invention is useful in conjunction with controlling thespread of damage from failure of passive components in a communicationsnetwork (such as broken optical fibers and/or severed coaxial cables),or in conjunction with controlling the spread of damage from failure ofactive components (such as data drop/add nodes and/or repeaters), or thelike. There are virtually innumerable uses for the invention, all ofwhich need not be detailed here.

[0063] All the disclosed embodiments of the invention described hereincan be realized and practiced without undue experimentation. Althoughthe best mode of carrying out the invention contemplated by theinventors is disclosed above, practice of the invention is not limitedthereto. Accordingly, it will be appreciated by those skilled in the artthat the invention may be practiced otherwise than as specificallydescribed herein.

[0064] For example, the individual components need not be assembled inthe disclosed configuration, but could be assembled in virtually anyconfiguration. Further, the individual components need not be fabricatedfrom the disclosed materials, but could be fabricated from virtually anysuitable materials. Further, although the splitter-combiner describedherein can be a physically separate module, it will be manifest that thesplitter-combiner may be integrated into the apparatus with which it isassociated. Furthermore, all the disclosed elements and features of eachdisclosed embodiment can be combined with, or substituted for, thedisclosed elements and features of every other disclosed embodimentexcept where such elements or features are mutually exclusive.

[0065] It will be manifest that various additions, modifications andrearrangements of the features of the invention may be made withoutdeviating from the spirit and scope of the underlying inventive concept.It is intended that the scope of the invention as defined by theappended claims and their equivalents cover all such additions,modifications, and rearrangements.

[0066] The appended claims are not to be interpreted as includingmeans-plus-function limitations, unless such a limitation is explicitlyrecited in a given claim using the phrase “means for.” Expedientembodiments of the invention are differentiated by the appendedsubclaims.

What is claimed is:
 1. An apparatus, comprising a communications link,said communications link including a splitter-combiner communicativelycoupled to a headend, said splitter-combiner including: a signalsplitter communicatively coupled to a headend input and communicativelycoupled to a downstream output; and signal combiner communicativelycoupled to said signal splitter, communicatively coupled to an upstreaminput, and communicatively coupled to a headend output; and a datadrop/add device communicatively coupled to said downstream output andcommunicatively coupled to said upstream input.
 2. The apparatus ofclaim 1, wherein said data drop/add device includes anoptical-to-electronic transducer coupled to said downstream output andan electronic-to-optical transducer coupled to said upstream input. 3.The apparatus of claim 1, wherein said splitter-combiner is a passivedevice.
 4. The apparatus of claim 1, further comprising anothersplitter-combiner communicatively coupled to said headend input andcommunicatively coupled to said headend.
 5. The apparatus of claim 4,further comprising another data drop/add device communicatively coupledto said another splitter-combiner.
 6. The apparatus of claim 1, whereinsaid communications link includes an optical fiber coupled between saidsplitter-combiner and said headend, said signal splitter includes anoptical beam splitter and said signal combiner includes an optical beamcombiner.
 7. The apparatus of claim 1, wherein said communications linkincludes a coaxial cable coupled between said splitter-combiner and saidheadend, said signal splitter includes an electrical splitter circuitand said signal combiner includes an electrical combiner circuit.
 8. Anapparatus, comprising a communications link, said communications linkincluding a first splitter-combiner communicatively coupled to aheadend, said first splitter-combiner including: a first signal splittercommunicatively coupled to a first headend input and communicativelycoupled to a first downstream output; and a first signal combinercommunicatively coupled to said first signal splitter, communicativelycoupled to a first upstream input, and communicatively coupled to afirst headend output; a data drop/add device communicatively coupled tosaid first downstream output and communicatively coupled to said firstupstream input; a second splitter-combiner communicatively coupledbetween said first headend input and said headend, said secondsplitter-combiner including: a second signal splitter communicativelycoupled to said headend and communicatively coupled to a seconddownstream output; and a second signal combiner communicatively coupledto said second signal splitter, communicatively coupled to a secondupstream input, and communicatively coupled to said first headend input.9. The apparatus of claim 8, wherein said data drop/add device includesan optical-to-electronic transducer coupled to said downstream outputand an electronic-to-optical transducer coupled to said upstream input.10. The apparatus of claim 8, wherein both said first splitter-combinerand said second splitter-combiner are passive devices.
 11. The apparatusof claim 8, further comprising a third splitter-combiner communicativelycoupled to said headend input and communicatively coupled between saidsecond splitter-combiner and said headend.
 12. The apparatus of claim11, further comprising another data drop/add device communicativelycoupled to said third splitter-combiner.
 13. The apparatus of claim 8,wherein said communications link includes an optical fiber coupledbetween said first splitter-combiner and said headend, said first signalsplitter includes an optical beam splitter and said first signalcombiner includes an optical beam combiner.
 14. The apparatus of claim8, wherein said communications link includes a coaxial cable coupledbetween said first splitter-combiner and said headend, said first signalsplitter includes an electrical splitter circuit and said first signalcombiner includes an electrical combiner circuit.
 15. A method,comprising deploying a communication link, at least a portion of whichis protected against active equipment failure, that includes asplitter-combiner communicatively coupled between a data drop/add deviceand a headend.
 16. The method of claim 15, further comprising switchingsaid splitter-combiner from a bypass state to a shunt state at asplitter-combiner when the data drop/add device is communicativelyde-coupled from the splitter-combiner.
 17. The method of claim 15,wherein said splitter-combiner includes: a signal splittercommunicatively coupled to a headend input and communicatively coupledto a downstream output; and a signal combiner communicatively coupled tosaid signal splitter, communicatively coupled to an upstream input, andcommunicatively coupled to a headend output, and wherein switchingresults from a communicative decoupling of said upstream input from saiddownstream output.
 18. The method of claim 17, wherein saidcommunications link includes a plurality of drop/add devices and saidsplitter-combiner is communicatively coupled between a first of saidplurality of drop/add devices and a second of said plurality of drop/adddevices, and said second of said plurality of drop/add devices iscommunicatively decoupled from said splitter-combiner, therebycommunicatively decoupling said upstream input from said downstreamoutput.
 19. The method of claim 15, further comprising monitoring aswitching state of said splitter-combiner.
 20. The method of claim 19,further comprising reporting said switching state to said headend. 21.The method of claim 20, further comprising recording said switchingstate as diagnostic data.
 22. The method of claim 15, further comprisingmeasuring a relative signal attenuation between a detected bypass signaland a detected shunt signal.
 23. The method of claim 22, furthercomprising changing a split ratio of the splitter-combiner.